The invention relates to a method for testing elongated objects having a non-circular cross-section by at least one test probe guided over a circular path or orbit around the object, as well as a testing apparatus for performing the method with a test head traversed by the object and which is provided with at least one test probe, which is guided on a circular path or orbit surrounding the object. The invention more particularly relates to the problem of continuously, uninterruptedly and non-destructively testing for surface defects, preferably directly after their manufacture, metallic semifinished products having a non-circular cross-section. Particular interest is attached to e.g. spring wires having an elliptical or oval cross-section, such as are used to an increasing extent in the construction of valve springs in car engine building.